diff --git a/src/dynamics/Body.ts b/src/dynamics/Body.ts
index c1ba7818..b04c706a 100644
--- a/src/dynamics/Body.ts
+++ b/src/dynamics/Body.ts
@@ -435,7 +435,7 @@ export class Body {
     // Touch the proxies so that new contacts will be created (when appropriate)
     const broadPhase = this.m_world.m_broadPhase;
     for (let f = this.m_fixtureList; f; f = f.m_next) {
-      for (let i = 0; i < f.m_proxies.length; ++i) {
+      for (let i = 0; i < f.m_proxyCount; ++i) {
         broadPhase.touchProxy(f.m_proxies[i].proxyId);
       }
     }
diff --git a/src/dynamics/Fixture.ts b/src/dynamics/Fixture.ts
index 9e1da02f..6147642e 100644
--- a/src/dynamics/Fixture.ts
+++ b/src/dynamics/Fixture.ts
@@ -128,6 +128,8 @@ export class Fixture {
   /** @internal */ m_shape: Shape;
   /** @internal */ m_next: Fixture | null;
   /** @internal */ m_proxies: FixtureProxy[];
+  // 0 indicates inactive state, this is not the same as m_proxies.length
+  /** @internal */ m_proxyCount: number;
   /** @internal */ m_userData: unknown;
 
   constructor(body: Body, def: FixtureDef);
@@ -162,7 +164,10 @@ export class Fixture {
     this.m_next = null;
 
     this.m_proxies = [];
+    this.m_proxyCount = 0;
 
+    // fixture proxies are created here,
+    // but they are activate in when a fixture is added to body
     const childCount = this.m_shape.getChildCount();
     for (let i = 0; i < childCount; ++i) {
       this.m_proxies[i] = new FixtureProxy(this, i);
@@ -367,12 +372,12 @@ export class Fixture {
    * These support body activation/deactivation.
    */
   createProxies(broadPhase: BroadPhase, xf: TransformValue): void {
-    _ASSERT && console.assert(this.m_proxies.length == 0);
+    _ASSERT && console.assert(this.m_proxyCount == 0);
 
     // Create proxies in the broad-phase.
-    const childCount = this.m_shape.getChildCount();
+    this.m_proxyCount = this.m_shape.getChildCount();
 
-    for (let i = 0; i < childCount; ++i) {
+    for (let i = 0; i < this.m_proxyCount; ++i) {
       const proxy = this.m_proxies[i];
       this.m_shape.computeAABB(proxy.aabb, xf, i);
       proxy.proxyId = broadPhase.createProxy(proxy.aabb, proxy);
@@ -381,14 +386,13 @@ export class Fixture {
 
   destroyProxies(broadPhase: BroadPhase): void {
     // Destroy proxies in the broad-phase.
-    for (let i = 0; i < this.m_proxies.length; ++i) {
+    for (let i = 0; i < this.m_proxyCount; ++i) {
       const proxy = this.m_proxies[i];
       broadPhase.destroyProxy(proxy.proxyId);
       proxy.proxyId = null;
-      proxy.fixture = null;
     }
 
-    this.m_proxies.length = 0;
+    this.m_proxyCount = 0;
   }
 
   /**
@@ -396,7 +400,7 @@ export class Fixture {
    * next transformation).
    */
   synchronize(broadPhase: BroadPhase, xf1: TransformValue, xf2: TransformValue): void {
-    for (let i = 0; i < this.m_proxies.length; ++i) {
+    for (let i = 0; i < this.m_proxyCount; ++i) {
       const proxy = this.m_proxies[i];
       // Compute an AABB that covers the swept shape (may miss some rotation
       // effect).
@@ -477,7 +481,7 @@ export class Fixture {
 
     // Touch each proxy so that new pairs may be created
     const broadPhase = world.m_broadPhase;
-    for (let i = 0; i < this.m_proxies.length; ++i) {
+    for (let i = 0; i < this.m_proxyCount; ++i) {
       broadPhase.touchProxy(this.m_proxies[i].proxyId);
     }
   }